Re: [PATCH v2] cxl/events: Return IRQ_NONE when no event is pending

[Anisa Su <anisa.su887@gmail.com>]

On Sat, Sep 12, 2026 at 03:08:15PM +0530, Shaikh Kamaluddin wrote:
> CXL event interrupts may share an MSI/MSI-X vector with other event
> logs or device features. Consequently, cxl_event_thread() is registered
> with IRQF_SHARED and must determine whether the event-log facility
> claimed the interrupt.
> 
> The handler masks the Device Event Status register to the event logs
> supported by the driver. However, when no supported status bit is set,
> it exits the processing loop and still returns IRQ_HANDLED. This
> incorrectly reports that the interrupt was claimed and prevents the
> generic spurious-interrupt detector from accounting it as unhandled.
> 
> Track whether the CXL event handler claimed the interrupt and return
> IRQ_NONE when no supported event is detected. If no handler sharing the
> vector claims a sustained interrupt storm, the generic spurious-
> interrupt detector can eventually identify and disable the affected
> IRQ.
> 
> Signed-off-by: Shaikh Kamaluddin <shaikhkamal2012@gmail.com>
Reviewed-by: Anisa Su <anisa.su@samsung.com>
> ---
> Changes in V2:
> - Emphasize that returning IRQ_NONE enables generic spurious-interrupt
>   detection and drop the Fixes tag. (Jonathan Cameron)
> - Check whether the event interrupt is already disabled by Anisa Su's
>   patch; no code changes were needed. (Ben Cheatham)

One thing I want to correct: The change requested was to say a
spurious IRQ will eventually be disabled in the commit message, not
check whether the event interrupts is already disabled...
See https://lore.kernel.org/linux-cxl/aqLZP3ORYzCLfSgR@acer-nitro-anv15-41/T/#m32c74ebf05eee9a3ee49c57dd24848db29919031
I do see that it's been added to the commit message though, so no need
to do anything.

Thanks,
Anisa
> - Rebase onto v7.3-rc2; no code changes.
> 
>  drivers/cxl/pci.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index c7c91e8dc51d..8b560cae91f2 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -515,6 +515,7 @@ static irqreturn_t cxl_event_thread(int irq, void *id)
>  	struct cxl_dev_id *dev_id = id;
>  	struct cxl_dev_state *cxlds = dev_id->cxlds;
>  	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlds);
> +	bool handled = false;
>  	u32 status;
>  
>  	do {
> @@ -527,11 +528,13 @@ static irqreturn_t cxl_event_thread(int irq, void *id)
>  		status &= CXLDEV_EVENT_STATUS_ALL;
>  		if (!status)
>  			break;
> +
> +		handled = true;
>  		cxl_mem_get_event_records(mds, status);
>  		cond_resched();
>  	} while (status);
>  
> -	return IRQ_HANDLED;
> +	return handled ? IRQ_HANDLED : IRQ_NONE;
>  }
>  
>  static int cxl_event_req_irq(struct cxl_dev_state *cxlds, u8 setting)
> 
> base-commit: df2908090cda368b01ff43709f51890076c56157
> -- 
> 2.43.0
>